Side gap press and frame structure therefor

ABSTRACT

Two parallel yokes separated by at least one column. The press frame is acted upon by an external frame comprising biased wires or tapes exerting on the column, or a portion adjacent the press tools, a considerably greater compressive pre-stressing load than that to which column or column portions at a greater distance from the tools are subjected.

United States Patent 1 Jonsson et al.

[ 1 SIDE GAP PRESS AND FRAME STRUCTURE THEREFOR [75] Inventors: Finn L. Jonsson; Sten Trolle, both of Ystad, Sweden [73] Assignee: AB Carbox, Ystad, Sweden [22] Filed: Jan. 19, 1972 [21] Appl. No.: 219,004

[30] Foreign Application Priority Data Nov. 26, 1971 Sweden 15213/71 [52] v US. Cl. 100/214 [51] Int. Cl B30b 1/00 [58] Field of Search 100/214, 231; 72/455; 7 83/859 [56] References Cited UNITED STATES PATENTS 586,353 '7/1897 De Armon 100/231 X 4 1 Apr. 2, 1974 1,085,296 l/l9l4 Perkins 100/231 3,064,558 I l/l962 Von Platcn 3,247,783 4/1966 Hammon 100/231 X 3,303,774 2/1967 Shiukawa 100/231 Primary Examiner-Billy .l. Wilhite Attorney, Agent, or Firm-Flynn & Frishauf 57] ABSTRACT Two parallel yokes separated by at least one column.

The press frame is acted upon by an external frame comprising biased wires or tapes exerting on the column, or a portion adjacent the press tools,va considerably greater compressive pre-stressing load than that to which column or column portions at a greater distance from the tools are subjected.

6 Claims, 1 Drawing Figure SIDE GAP PRESS AND FRAME STRUCTURE THEREFOR BACKGROUND OF THE INVENTION The frame of so called gap presses or goose-necked presses can be defined as having generally the configuration of a U with horizontal legs, the vertical web portion of the U corresponding to the single column of the frame. Such frames can either be cast or assembled by welding and their press tools are mounted between the mutually apposed free ends of the horizontal legs. The primary advantage of such a configuration is that the space at disposal around the press tools is limited by the sole column only which means that the press can be used also for very large work pieces.

On the other hand the geometry of the frame above described also implies significant disadvantages relating to the strength properties of the frame and arising due to the fact that the horizontal as well as the vertical frame portions are subjected to bending stresses. Moreover, where those portions meet in the comers there arise tensile stresses resulting in very high stress concentrations.

The most concrete consequence of the bending stresses appears as a highly undesired deformation of the frame when the press is in operation. The net result of the corresponding bending forces will be that the centre axes of the upper press tool, e.g., a hydraulic ram, and the lower press tool, for instance, a die, do not stay coaxial but will deviate from each other by a small angular amount. This does naturally negatively affect the precision attainable when working with the press.

The high stress concentration in the corners, a phenomenon often referred to as the comer effect involves a very high risk of material fatigue which in turn results in cracks or fractures increasing the operational costs by necessitating repair works and corresponding operational shut-downs.

For the reasons above mentioned it has in gap-type presses been extremely difficult to reach higher press forces than about 1,000-1 ,500 tons.

Also in conventional column presses having a closed frame, i.e., one column at each end of the horizontal frame portions, or yokes, similar disadvantages appear even if less pronounced. However, the corner effect may still cause serious problems and considerable damage. The prior art has for a few decades been aware of a special type of this closed-frame press in which the corner effect has been totally eliminated. The frame of a press of such a type comprises two parallel horizontal yokes spaced by two columns located at the yoke ends so that there is defined a square opening housing the tools. The parts of the frame the yokes and the columns are surrounded and held together by a bandage" consisting of biased steel wires wound around the frame in several turns and layers and subjecting it to forces tending to keep thecolumns biased by a pressure load which is in the operation of the press to a great extent balanced by the outwardly acting reactional forces set up at the pressing tools. It is realized that thanks to the fact that'there is a certain pressure load on the columns also when the press operates at its maximum working pressure no tensile stresses can be generated at the corners between the columns and the yokes. On the other hand it is evident that since the press tools will have to be located in the opening between the columns the capacity of the press to handle SUBJECT MATTER OF THE INVENTION Briefly, a pair of parallel yokes are separated by at least one column. An external frame is located to exert on the column, or a portion which is closest to the press tool, a compressive pre-stressing load which is greater than that to which the column, or the portion adjacent the press tool, is subjected when the press is in operation. By pre-stressing the column, or the portion of the column closest to the tools under compression, reactive forces arising in operation of the press, are compensated.

DESCRIPTION OF THE DRAWING One embodiment of the invention is described below, reference being made to the accompanying drawing showing, partly in section, a perspective view of a hydraulic press for high pressures designed in accordance with the teachings of this invention.

The press illustrated in the drawing has a frame supported by a base consisting of two extended feet I and 2. The frame proper comprises a lower horizontal yoke 3 and an upper horizontal yoke 4, the two yokes being spaced by two vertical columns 5 and 6. As appears from the drawing, column 5 is located between two opposed ends of yokes 3 and 4 whereas column 6 is centrally located between the two ends of each yoke. In this way a free space is formed at the other'two yoke ends where the tools of the press have been mounted. According to the illustrated embodiment those tools are constituted by a lower die 7 mounted on yoke 3 and by a ram 8 reciprocable within a hydraulic cylinder 9 suspended from the upper yoke 4. Reference numerals l0 and ll designate piping for supplying hydraulic fluid to cylinder 9 which, as is realized, should be doubleacting.

The press here illustrated differs from prior arthigh pressure equipment in having one of its columns displaced from the'yoke ends to a central portion. However, the invention does also have a second important main characteristic residing therein that its external reinforcing frame 12 is rotated through as compared with the prior art machines. Stated in other words this means that frame 12 is mounted crosswise relatively to the longitudinal plane of the frame 3-6. It does also appear from the drawing that frame 12 surrounds column 6. Between the top surface of yoke 4 and the inner curved wall of the substantially oval reinforcing frame 12 there is inserted a piece 13 matching the contour of yoke 4 to that of frame 12 thus distributing evenly the forces transferred from frame 12 to yoke 4. Finally, reference numeral 14 refers to biased wires, tapes or the like which form the active parts of reinforcing frame 12.

An inspection of the drawing will indicate that the combination of the two features above referred to results in the simultaneous realization of two inherently opposite technical advantages, a press which can both handle large work pieces and operate with high press forces. In operation the frame 12 and column 5 provide the necessary reactional strength while at the same time eliminating the corner effects. In a practical situation this can mean that the tension in wires 14 which in response to the bias thereof .was initially about 70,000 psi is increased to e.g., 1 10,000 psi. The central column 6 could then typically be subjected to an initial compression stress of the order of magnitude 35,000 psi which, upon application of the press force at the tools, approaches meaning that all of the compression is lifted off from that column. At the same time the compression stress in column which was initially 0 is increased to about 35,000 psi. However, in the practical working of this invention the parameters here discussed are selected so that neither of columns 5 and 6 is at any time completely without compression but always subjected to a compression stress of at least 7,000 psi which is preferred to guarantee the rigidity of the various components 36 of the press frame.

As was indicated above it does per se belong to the art to provide presses designed for high operational pressures with an external frame or bandage corresponding to the reinforcing arrangement here described. However, in those prior art presses the longitudinal plane of symmetry of that frame has invariably coincided with that of the press frame proper and the press tools have been located centrally in respect of the yokes between two lateral columns. When compared with such a known frame work the subject of this invention could be said to be characterized by interchange of the press tools and one of the columns. It should also be noted that a press of the known configuration is not a gap press since its tools are not located at free yoke ends but centrally between two columns.

The reinforcing frame according to this invention can be constituted by any suitable arrangement designed and mounted so that it may'perform the function here described. More specifically, that function could be described in the following way. The column, or column portion, located at the shortest distance from the press tools is initially subjected to a compression load which is considerably reduced but not completely eliminated in response to the forces tending to deform the yokes and generated upon application of the press force at the tools. In this way the different portions of the frame are positively held together and, what is still more important, the column or column portion concerned is effectively protected from tensile stresses which could cause the inconveniences and disadvantages above referred to. The biased reinforcing frame does not have to be oval in shape. By way of example it could be constituted by beams mounted crosswise outside the yokes and having their ends interconnected by biasing means which could in turn be loop-shaped. It is also obvious that terms such as vertical and U-shaped have been used for the purpose of illustration only and do not define the scope of the invention it being fully apparent that the invention is applicable also at presses the various components of which are shaped and mounted otherwise than according to the preferred embodiment here described.

What we claim is:

1. A side gap press having a frame structure, comprising a pair of parallel yokes (3, 4) having, each, a support end and a tool receiving end;

at least one column (5) holding said yokes in spaced position and located remote from the tool receiving ends of the yokes;

means mounting press tools at the tool receiving end of said yokes;

biasing means (12, 14) to subject the column in a location nearest the tool receiving ends of the yokes to a force which in the inoperative state of the press, subjects said column in said nearest location to a compression force which is greater than the compression force on the column in a location remote from the tool receiving ends of the yokes, said bias means comprising tension means biased under tension and holding together said yokes and column and maintaining the frame column biased under compression also in the operative state of the press, said biasing means forming an outer frame located crosswise relatively to a vertical plane of symmetry through a press frame.

2. A side gap press as claimed in claim 1, wherein the outer frame is located at right angles with respect to the vertical plane of symmetry.

3. A side gap press as claimed in claim 1, wherein the tension means comprises wires.

4. A side gap press as claimed in claim 1, wherein at least two columns (5, 6) are provided, one column (5) being located at the support ends of the yokes (3, 4) and the other column (6) being located intermediate the ends of the yokes, the tension means (12, 14) biasing said other column (6) located intermediate the ends of the yokes to a compressive force which is greater than the compressive force exerted on said one column (5).

5. A side gap press as claimed in claim 4, and wherein the tension means (12, 14) are located with respect to the yoke essentially in the location of the other column (6).

6. A side gap press as claimed in claim 1, wherein the tension means are located intermediate ends of the 

1. A side gap press having a frame structure, comprising a pair of parallel yokes (3, 4) having, each, a support end and a tool receiving end; at least one column (5) holding said yokes in spaced position and located remote from the tool receiving ends of the yokes; means mounting press tools at the tool receiving end of said yokes; biasing means (12, 14) to subject the column in a location nearest the tool receiving ends of the yokes to a force which in the inoperative state of the press, subjects said column in said nearest location to a compression force which is greater than the compression force on the column in a location remote from the tool receiving ends of the yokes, said bias means comprising tension means biased under tension and holding together said yokes and column and maintaining the frame column biased under compression also in the operative state of the press, said biasing means forming an outer frame located crosswise relatively to a vertical plane of symmetry through a press frame.
 2. A side gap press as claimed in claim 1, wherein the outer frame is located at right angles with respect to the vertical plane of symmetry.
 3. A side gap press as claimed in claim 1, wherein the tension means comprises wires.
 4. A side gap press as claimed in claim 1, wherein at least two columns (5, 6) are provided, one column (5) being located at the support ends of the yokes (3, 4) and the other column (6) being located intermediate the ends of the yokes, the tension means (12, 14) biasing said other column (6) located intermediate the ends of the yokes to a compressive force which is greater than the compressive force exerted on said one column (5).
 5. A side gap press as claimed in claim 4, and wherein the tension means (12, 14) are located with respect to the yoke essentially in the location of the other column (6).
 6. A side gap press as claimed in claim 1, wherein the tension means are located intermediate ends of the yokes. 